Copyright (c) 2015, 2016 Google, Inc and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
  Stefan Xenos (Google) - Initial implementation
/*******************************************************************************
 * Copyright (c) 2015, 2016 Google, Inc and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *   Stefan Xenos (Google) - Initial implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.core.nd.field;

import org.eclipse.jdt.internal.core.nd.INdStruct;
import org.eclipse.jdt.internal.core.nd.Nd;
import org.eclipse.jdt.internal.core.nd.NdNode;
import org.eclipse.jdt.internal.core.nd.db.ModificationLog;
import org.eclipse.jdt.internal.core.nd.db.ModificationLog.Tag;
import org.eclipse.jdt.internal.core.nd.db.Database;

Represents a 1-to-0..1 relationship in a Nd database.
/**
 * Represents a 1-to-0..1 relationship in a Nd database.
 */
public class FieldOneToOne<T extends INdStruct> extends BaseField implements IDestructableField, IRefCountedField {
	public final StructDef<T> nodeType; 
	FieldOneToOne<?> backPointer;
	private boolean pointsToOwner;
	private final Tag putTag;
	private final Tag destructTag;

	
Params:
nodeType – 
backPointer – /**
	 * @param nodeType
	 * @param backPointer
	 */
	private FieldOneToOne(StructDef<T> nodeType, FieldOneToOne<?> backPointer, boolean pointsToOwner) {
		this.nodeType = nodeType;

		if (backPointer != null) {
			if (backPointer.backPointer != null && backPointer.backPointer != this) {
				throw new IllegalArgumentException(
					"Attempted to construct a FieldOneToOne referring to a backpointer list that is already in use" //$NON-NLS-1$
						+ " by another field"); //$NON-NLS-1$
			}
			backPointer.backPointer = this;
		}
		this.backPointer = backPointer;
		this.pointsToOwner = pointsToOwner;
		setFieldName("field " + nodeType.getNumFields() + ", a " + getClass().getSimpleName() //$NON-NLS-1$//$NON-NLS-2$
				+ " in struct " + nodeType.getStructName()); //$NON-NLS-1$
		this.putTag = ModificationLog.createTag("Writing " + getFieldName()); //$NON-NLS-1$
		this.destructTag = ModificationLog.createTag("Destructing " + getFieldName()); //$NON-NLS-1$
	}

	public static <T extends INdStruct, B extends INdStruct> FieldOneToOne<T> create(StructDef<B> builder,
			StructDef<T> nodeType, FieldOneToOne<B> forwardPointer) {

		FieldOneToOne<T> result = new FieldOneToOne<T>(nodeType, forwardPointer, false);
		builder.add(result);
		builder.addDestructableField(result);
		return result;
	}

	public static <T extends INdStruct, B extends INdStruct> FieldOneToOne<T> createOwner(StructDef<B> builder,
			StructDef<T> nodeType, FieldOneToOne<B> forwardPointer) {

		FieldOneToOne<T> result = new FieldOneToOne<T>(nodeType, forwardPointer, true);
		builder.add(result);
		builder.addDestructableField(result);
		builder.addOwnerField(result);
		return result;
	}

	public T get(Nd nd, long address) {
		long ptr = nd.getDB().getRecPtr(address + this.offset);
		return NdNode.load(nd, ptr, this.nodeType);
	}

	public void put(Nd nd, long address, T target) {
		Database db = nd.getDB();
		db.getLog().start(this.putTag);
		try {
			cleanup(nd, address);
			if (target == null) {
				db.putRecPtr(address + this.offset, 0);
				if (this.pointsToOwner) {
					nd.scheduleDeletion(address);
				}
			} else {
				db.putRecPtr(address + this.offset, target.getAddress());
				db.putRecPtr(target.getAddress() + this.backPointer.offset, address);
			}
		} finally {
			db.getLog().end(this.putTag);
		}
	}

	@Override
	public void destruct(Nd nd, long address) {
		Database db = nd.getDB();
		db.getLog().start(this.destructTag);
		try {
			cleanup(nd, address);
		} finally {
			db.getLog().end(this.destructTag);
		}
	}

	private void cleanup(Nd nd, long address) {
		Database db = nd.getDB();
		long ptr = db.getRecPtr(address + this.offset);
		if (ptr != 0) {
			db.putRecPtr(ptr + this.backPointer.offset, 0);
			// If we own our target, delete it
			if (this.backPointer.pointsToOwner) {
				nd.scheduleDeletion(ptr);
			}
		}
	}

	@Override
	public int getRecordSize() {
		return Database.PTR_SIZE;
	}

	@Override
	public boolean hasReferences(Nd nd, long address) {
		if (this.pointsToOwner) {
			long ptr = nd.getDB().getRecPtr(address + this.offset);
			return ptr != 0;
		}
		return false;
	}
}